Cool, I'm glad I'm not the only person that's had these kinds of ambitions. My wife says it "must be a guy thing" to want to "control" stuff
I realize I could have a coaltrol and have more free time, but I enjoy the challenge of a project like this, which is well suited for winter time since I can't work on any outdoor projects...
I actually have this system working, so I'm past the theory stage. I am currently using an older HP PC (<1ghz) as a dedicated controller running a fresh, clean install of XP. XP is actually pretty stable as long as you don't have tons of stuff installed on it (though if I had the knowledge, I'd rather do it with a Linux...but alas) As for some of your other concerns...it will not have internet connectivity so auto updates/reboots are no problem. Currently my program is set to load at startup so if there is a power failure, the PC will reboot automatically and with only the OS loading, it boots to desktop in under 30 seconds. All important variables are written to disk every time the program cycles through the control loop, so upon reboot the program can "pick up where it left off". Though all that asided, a UPS is in my long-term plans.
The interface I use is a Phidget (http://www.phidgets.com
) which has digital and analog inputs and digital outputs and connects to the PC via USB. That is really the key piece to my setup and w/o that I wouldn't be able to do this. The second key piece is that I was able to use the Phidget C+ API with Clarion (Clarion is a somewhat obscure, but very powerful language I program in and is the only language I have any skill in these days). I do think that Arduino piece looks nice and if I wasn't already commited with this particular setup, I probably would consider it. Another setup I did consider was using MS Robotics Studio, but after my initial tests with Clarion were successful, I abandoned that idea quickly since it would've meant learning a whole new language.
Regarding the blower control, I am using the Phidget interface to turn the fans and pusher motor on and off using solid-state relays I pulled from old copiers (which are a treasure trove of components
) I don't plan on trying to modulate the speed of the fans, only turn them on/off for variable periods of time. I think the Phidget interface can turn on/off it's outputs pretty quickly so theoretically I could control the speed by turning them off/on rapidly but I'm not sure that would be good for the motor. Old copiers also have a multitude of 24v DC fans which could be modulated by voltage but unfortunately, Phidgets does not make an interface with analog outputs so I currently have no way of controlling devices other than with on/off.
eelhc, I do plan on using a thermal probe to regulate the stove temperature, however my goal is to regulate it in relation to the outside temperature (as well as the inside) and run the distribution blower constantly. I feel like if the stove is producing heat and I'm not utilizing it, then it is being wasted, so I'd rather lower the stove temperature when less heat is needed and keep the blower constant than vice versa. Although I may change that idea once I install the DHW coil.